WO2019090884A1

WO2019090884A1 - Polymerization process of impact polypropylene

Info

Publication number: WO2019090884A1
Application number: PCT/CN2017/115400
Authority: WO
Inventors: 刘立新; 李泽民; 张毅; 刘利妍; 吴霞
Original assignee: 北京华福工程有限公司
Priority date: 2017-11-10
Filing date: 2017-12-11
Publication date: 2019-05-16
Also published as: CN109776703A

Abstract

A method for preparing an impact polypropylene, comprising: (1) performing propylene prepolymerization of a liquid phase propylene with a polymerization catalyst, to be a feedstock slurry containing a propylene prepolymer, wherein the prepolymerization temperature is 40ºC-45ºC, the prepolymerization pressure is 3.2-3.9 MPaG, and the main catalyst is 0.02 weight %-0.05 weight % of the liquid phase propylene; (2) mixing the feedstock slurry, a recovered liquid phase propylene and hydrogen gas into a liquid phase polymeric raw material; and then successively carrying out a liquid phase homopolymerization of propylene and a gas phase homopolymerization of propylene, to obtain a product containing polypropylene; (3) separating the product containing polypropylene, and subjecting the separated polypropylene to a copolymerization reaction with ethylene and a second propylene to obtain an impact polypropylene. The present method reduces energy consumption per unit product, and propylene loss.

Description

Polymerization method of impact polypropylene

Technical field

The present invention relates to the field of propylene ethylene copolymerization, and in particular to a method for polymerizing impact polypropylene.

Background technique

Polypropylene is a polymer made of propylene as a monomer. It is a very important variety in general-purpose plastics. It is rich in raw materials, low in price, easy to process and form, non-toxic, etc. It can also be copolymerized, blended, Modification and other measures for modification have a very broad application field. Among polyolefin resins, it is second only to polyethylene and the second largest plastic. However, the impact resistance of polypropylene is not so good and needs to be improved to improve impact resistance.

At present, the process technologies for producing polypropylene at home and abroad mainly include a liquid phase bulk method, a gas phase bulk method, and a polymerization method in which a liquid phase body and a gas phase body are connected in series. Depending on the type of reactor, it can be divided into Spheripol, Gasoline Fluidized Bed (Unipol), Vertical Stirred Tank Process (Novolen, Hypol), Horizontal Stirred Tank Process (Inoes, JPP) and different The method of combining the reactor phases.

In the polypropylene production process, the propylene monomer is polymerized in a polymerization reactor under the action of a main catalyst, an activator, and an electron donor to obtain a polypropylene slurry or a solid material. The resulting polypropylene is further subjected to flash degassing, catalyst deactivation, drying and nitrogen displacement to obtain a polypropylene powder product. The propylene gas entrained in the reactor discharge process is returned to the reaction system for recycling after low-pressure washing, gas compression, and light gas separation, thereby reducing the consumption of raw materials propylene and hydrogen.

At present, polypropylene processes at home and abroad have different advantages and disadvantages:

Batch process bulk polymerization process: The propylene polymerization process independently developed by China has the advantages of short process, low investment and quick effect. Its shortcomings are high process energy consumption, low automation, unstable product quality and large monomer consumption.

Lyondell Basell's Spheripol process: a loop reactor with forced circulation of an axial flow pump, liquid phase bulk polymerization, and heat removal by a jacket outside the loop. The advantages are that the reaction conditions are relatively easy to control, the heat transfer coefficient of the reactor is large, the yield per unit volume is high, the product performance is stable, the range of the brand is wide, and the gas phase reactor is used to produce high impact copolymerization products.

Grace's Unipol process: gas phase fluidized bed reactor, polymerization heat depends on the gas tropical tropics, the gas circulation is large, and it needs a high-powered booster fan to achieve the full mixing type, and the product quality is not uniform. The utility model has the advantages of suitable for copolymerization of ethylene and propylene, simple process, good physical property of the product, wide coverage of the brand, and a high-impact copolymer product with a second gas phase reactor.

INEOS's Innovene process: using a horizontal stirred reactor and a high performance INcat CDi catalyst, the reactor is close to the plug flow reactor, using liquid phase propylene vaporization to remove heat. The advantages are high reactor heat removal efficiency, stable production operation, uniform material residence time period during the reaction period, wide range of product melting index and low energy consumption.

Mitel's Hypol process in Japan: liquid phase bulk and gas phase bulk combined process to produce polypropylene, the first two reactors are vertical stirred tanks, the latter two are vertical gas fluidized bed polymerization tanks; the advantages of which can produce random copolymerization Block copolymer product; its shortcomings are long process, low equipment efficiency, gas phase reaction is full mixed type, product quality is not uniform, catalyst adaptability is poor, and the scale of the device is small; in recent years, there is no new Hypol process device in China.

SPG process: liquid phase bulk and gas phase bulk combination process, gas phase kettle is horizontal with stirred tank, the advantages are short process, low investment, low energy consumption, but can not produce high impact copolymerization products.

However, in the industrial implementation process of the above various processes, there are defects in the high energy consumption per unit of producing polypropylene, which in turn affects other reactions that may be subsequently extended, affecting the quality and stability of the polymer product, and the safety of the operation of the device. Sex, increase the investment in industrialization of the project and affect the economic benefits of the project.

Summary of the invention

The object of the present invention is to solve the problem of how to improve the impact resistance of polypropylene, reduce the unit energy consumption of the polypropylene production process, improve the quality and stability of the product, and the safety of the operation of the device, and reduce the loss of propylene. A method of polymerizing polypropylene. The method adopts a four-stage continuous polymerization process including propylene prepolymerization, propylene liquid phase bulk polymerization, propylene vapor phase bulk polymerization, and copolymerization of polypropylene with ethylene and propylene, which can realize mild prepolymerization of propylene, reduce catalyst dosage, and satisfy propylene polymerization. The requirements of the product product reduce the unit energy consumption and propylene loss in the industrial implementation of the entire process, and improve the economical efficiency of propylene industrial production. And copolymerizing polypropylene with ethylene gives a copolymer which has better impact resistance than polypropylene.

In order to achieve the above object, the present invention provides a polymerization method of impact polypropylene, which comprises:

(1) the first propylene is compressed into liquid phase propylene, and mixed into a polymerization catalyst, and then fed to a prepolymerization reactor for prepolymerization of propylene to obtain a raw material slurry containing a propylene prepolymer;

Wherein, the prepolymerization temperature is 40 to 45 ° C, and the prepolymerization pressure is 3.2 to 3.9 MPaG;

The polymerization catalyst comprises a main catalyst, an activator and an electron donor, the main catalyst being used in an amount of 0.02 to 0.05% by weight of the liquid phase propylene;

(2) mixing the raw material slurry, the recovered liquid phase propylene and the recycled circulating hydrogen into a liquid phase polymerization raw material, and feeding it into a liquid phase polymerization tank for liquid phase homopolymerization of propylene to obtain a polypropylene slurry; Continuously input into the gas phase polymerization reactor, and the propylene in the polypropylene slurry is subjected to gas phase homopolymerization of propylene to obtain a polypropylene-containing product;

(3) The polypropylene-containing product is separated, and the separated polypropylene is copolymerized with ethylene and a second propylene to obtain impact polypropylene.

Preferably, in the step (1), the activator and the electron donor are used in an amount of 0.2 to 0.4% by weight and 0.04 to 0.06% by weight, respectively, of the liquid phase propylene.

Preferably, in the step (1), the liquid phase propylene pressure is 4 to 4.5 MPaG, and the liquid phase propylene temperature is 40 to 45 °C.

Preferably, the residence time of the propylene prepolymerization is 4 to 5 min.

Preferably, the propylene prepolymer is a polypropylene having a polymerization ratio of 50 to 100 times.

Preferably, in step (2), the concentration of the polypropylene in the liquid phase polymerization raw material is 150-300 g / L; the amount of the recovered liquid phase propylene is 25-30% by weight of the liquid phase propylene; The amount of hydrogen added is 0.04 to 0.3 kg with respect to 1000 kg of polypropylene in the liquid phase polymerization raw material.

Preferably, in the step (2), the liquid phase homopolymerization temperature of the propylene is 65 to 70 ° C, the liquid phase homopolymerization pressure of the propylene is 3 to 3.8 MPaG, and the residence time of the liquid phase homopolymerization of the propylene is 35 to 45 minutes.

Preferably, in the step (2), the propylene liquid phase is homopolymerized in a liquid phase polymerization vessel with an external cooler, and the propylene liquid phase is homogenized by partially vaporizing the liquid phase propylene. Part of the reaction heat is removed.

Preferably, the vaporized propylene gas is condensed or compressed and returned to the propylene liquid phase for homopolymerization as a first condensate or a first recycle propylene gas.

Preferably, in the step (2), the gas phase homopolymerization temperature of the propylene is 70 to 85 ° C, the gas phase homopolymerization pressure of the propylene is 2.6 to 2.8 MPaG, and the residence time of the gas phase homopolymerization of the propylene is 45 to 60 minutes.

Preferably, in the step (2), the gas phase polymerization reactor is a horizontal reactor with an external cooler, and the amount of the polypropylene slurry in the gas phase polymerization reactor is the gas phase polymerization reaction. 35 to 60% by volume of the device.

Preferably, the unreacted propylene gas discharged from the gas phase polymerization reactor is condensed or compressed and returned to the propylene gas phase homopolymerization as a second condensate or a second recycle propylene gas.

Preferably, in the step (3), the amount of ethylene added is 8 to 15% by weight of the liquid phase propylene, the second amount of propylene is 15 to 20% by weight of the liquid phase propylene; and the copolymerization temperature is 65. ～80 ° C, the copolymerization pressure is 2 to 2.4 MPaG, and the copolymerization reaction time is 30 to 60 min.

Preferably, in the step (3), the separation is carried out by a gas-solid separator of a series air lock mechanism at a pressure of 2 to 3 MPaG.

Through the above technical solution, a four-stage polymerization production process coupled with liquid phase prepolymerization of propylene, liquid phase bulk polymerization of propylene, vapor phase bulk polymerization of propylene and copolymerization of polypropylene and ethylene is provided for industrial production of impact polypropylene. The first three stages are homopolymerized to propylene, and then copolymerized with ethylene and propylene to obtain impact polypropylene. By this process, the conditions of propylene prepolymerization and feed control can be improved. Specifically, the propylene prepolymerization can be carried out at 40 to 45 ° C and 3.2 to 3.9 MPaG, which is more than the conditions of 5 to 10 ° C of the prior art. To be gentle. Thus, in the feed control, the propylene feed does not need to condense to below zero temperature, saving the condensation step.

In addition, the method provided by the present invention can also achieve a reduction in the amount of the main catalyst added, and a reduction in the amount and cost of the catalyst. Moreover, the addition of the polymerization catalyst can be carried out all at once from the prepolymerization, without the need to add a catalyst as in the prior art, which simplifies the operation steps and reduces fluctuations in the polymerization process.

Further, in the method provided by the present invention, the polymerization homopolypropylene stage can realize that the liquid phase propylene primary feed all participates in the propylene prepolymerization, and the raw material slurry containing the better dispersed propylene prepolymer is obtained, and the polymerization has a suitable polymerization multiple. Propylene facilitates the uniformity of subsequent coupled liquid phase, gas phase polymerization, and copolymerization to improve the quality of the polymer product. Unreacted propylene gas is recycled and reused throughout the process to reduce propylene losses.

The method provided by the invention can reduce the production energy consumption and propylene loss of the unit impact polypropylene product. It has been determined that the unit energy consumption of the product is less than 50kg standard oil/ton impact polypropylene, and the lowest is 40kg standard oil/ton impact polypropylene. The processing cost per unit product is about 1/2 of the same type of imported technology products of the same scale. In addition, the method provided by the invention can avoid the occurrence of local hot spots and explosions in the reaction, reduce the probability of plasticized blocks appearing in the product, and the product particles are not easily broken. The polymerization reaction adopts the liquid phase propylene vaporization to remove heat, the propylene recycling amount is small, the system does not need large-scale circulation equipment, can effectively reduce the equipment investment, the construction period is short, and the economy is better.

The impact polypropylene obtained by the method provided by the invention contains an elastomer component, the content of up to 46% by weight, can improve the toughness of the polypropylene, and is not easy to break at a low temperature (-23 ° C), and the measured impact strength of the notched simply supported beam high. The general homopolypropylene does not contain an elastomer component, has high rigidity, large brittleness, and poor toughness.

DRAWINGS

1 is a schematic view showing the process flow of producing impact polypropylene according to the present invention.

Description of the reference numerals

201-prepolymerization kettle 202-liquid phase polymerization reactor 203-gas phase polymerization reactor

204-copolymer kettle 211-first propylene condenser 212-first condensate separation tank

213-First cycle fan 214-Vaporizer propylene condenser 215-Vaporizer propylene cooler

216-first propylene condensate pump 217-gas-solid separator 218-air lock

219-Second propylene condenser 220-Second condensate separation tank 221-Second propylene condensate pump

222-Second circulation fan 100-line 101-slurry line

102-cycle line 103-polypropylene slurry line

Detailed ways

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to include values that are close to the ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and the individual point values, and the individual point values can be combined with one another to yield one or more new ranges of values. The scope should be considered as specifically disclosed herein.

The invention provides a polymerization method of impact polypropylene, and the process flow is shown in FIG. 1 , the method comprises:

(1) compressing the first propylene into liquid phase propylene, mixing it into a polymerization catalyst, and feeding it to a prepolymerization reactor for prepolymerization of propylene to obtain a raw material slurry containing polypropylene having a polymerization ratio of 50 to 100 times;

(3) separating the polypropylene-containing product, and copolymerizing the separated polypropylene with ethylene and second propylene to obtain impact polypropylene.

In the method provided by the present invention, the steps (1) and (2) are used to obtain a homopolypropylene, and then the homopolypropylene is copolymerized with ethylene and propylene by the step (3) to obtain an impact polypropylene. Steps (1) and (2) are carried out by a three-stage reaction of propylene prepolymerization, liquid phase bulk polymerization and gas phase bulk polymerization to realize prepolymerization of propylene homopolymerized raw material liquid phase propylene, which can reduce the amount of polymerization catalyst and It is advantageous to obtain a uniformly dispersed prepolymerized polypropylene. Moreover, it is not necessary to condense and batch feed the propylene raw materials, and then assist in the liquid phase bulk polymerization and the gas phase bulk polymerization in the respective polymerization processes, using propylene liquefaction to remove heat and reuse unreacted propylene materials, and corresponding polymerization conditions, the entire process is In the industrialization process of polymerizing impact polypropylene, the unit energy consumption of the production of impact polypropylene is reduced, the loss of propylene raw materials in the production process is reduced, and the production cost of propylene polymerization is reduced.

In the present invention, the step (1) first completes the prepolymerization of the liquid phase propylene. In this step, the combined prepolymerization combined with the liquid phase bulk polymerization and the gas phase bulk polymerization can carry all the liquid phase propylene into the prepolymerization reaction, and can be different from the prior art, only part of the propylene is prepolymerized and the other part is entered. Liquid phase bulk polymerization. Moreover, the polymerization catalyst can be added all at once, which simplifies the feed control, reduces the amount of the catalyst, and can form a more uniform prepolymer. Preferably, in the step (1), the liquid phase propylene pressure is 4 to 4.5 MPaG, and the liquid phase propylene temperature is 40 to 45 °C.

The condensation step and equipment for propylene are reduced in step (1), reducing the energy consumption of the process of the invention.

In the present invention, the propylene prepolymerization may be carried out as long as it provides a polypropylene which satisfies the polymerization ratio. Preferably, in the step (1), the residence time of the propylene prepolymerization is 4 to 5 minutes.

In the present invention, not only the entire liquid phase propylene participates in the prepolymerization reaction, but also the propylene prepolymer is better dispersed, and the propylene prepolymer is a polypropylene having a polymerization ratio of 50 to 100 times, which is advantageous for the subsequent step (2). The reaction process of liquid phase homopolymerization of propylene and gas phase homopolymerization of propylene is more stable, which is beneficial to reduce production energy consumption and propylene loss.

In the present invention, the polymerization catalyst may include a main catalyst, an activator, and an electron donor. The main catalyst may be a Ziegler-Natta catalyst system, for example, selected from a titanium-based propylene polymerization catalyst, which is a known material, which is commercially available, such as a catalyst of the domestic grade CS-1; the activator is selected from three Ethyl aluminum; the electron donor is selected from cyclohexylmethyldimethoxysilane (hereinafter referred to as "silane"). The liquid phase propylene can simultaneously serve as a carrier for the main catalyst, the activator and the electron donor, and the main catalyst, the activator and the electron donor are mixed into the liquid phase propylene to enter the prepolymerization tank to carry out the propylene prepolymerization. In the method provided by the present invention, prepolymerization is carried out at 40 to 45 ° C and 3.2 to 3.9 MPaG, and the amount of the main catalyst can be reduced. Preferably, in the step (1), the activator and the electron donor are used in an amount of 0.2 to 0.4% by weight and 0.04 to 0.06% by weight, respectively, of the liquid phase propylene.

In the present invention, in order to facilitate the operation, the amount of each material charged in the entire method is defined based on the amount of the liquid phase propylene charged into the prepolymerization.

In the present invention, the pre-polymerization kettle can be selected from a vertical tank reactor with stirring and jacketing, or a small loop tube with a cooling jacket, and the heat exchange area of the jacket area or the inner cooling tube must satisfy the pre-polymerization. The heat removal requirement of the reaction can be.

In the present invention, the propylene prepolymerization which is completed under the condition of the step (1), the obtained raw material slurry can be further subjected to homopolymerization of propylene to obtain a polypropylene by further combining liquid phase bulk polymerization and gas phase bulk polymerization. The raw material slurry contains a prepolymerized propylene prepolymer, unreacted liquid phase propylene, and a main catalyst, an activator and an electron donor which have not lost activity. Step (2) may be used to prepare a material for subsequent liquid phase and gas phase polymerization, and the liquid phase propylene and hydrogen may be recovered into the raw material slurry to obtain the liquid phase polymerization raw material, and the composition thereof satisfies the continuous liquid phase polymerization and gas phase of propylene. Polymerization, the entire process reduces unit energy consumption and propylene loss in polypropylene production. Preferably, in step (2), the concentration of the polypropylene in the liquid phase polymerization raw material is 150-300 g / L; the amount of the recovered liquid phase propylene is 25-30% by weight of the liquid phase propylene; The amount of hydrogen added is 0.04 to 0.3 kg with respect to 1000 kg of polypropylene in the liquid phase polymerization raw material. The amount of the recovered liquid phase propylene and hydrogen can be adjusted to satisfy the above conditions.

In the present invention, the step (2) is carried out to produce a propylene homopolymer product. Preferably, the liquid phase homopolymerization temperature of the propylene is 65 to 70 ° C, the liquid phase homopolymerization pressure of the propylene is 3 to 3.8 MPaG, and the residence time of the liquid phase homopolymerization of the propylene is 35 to 45 minutes.

In the present invention, the liquid phase homopolymerization of propylene carried out in the step (2), and the heat of reaction released during the polymerization is removed in time to facilitate the production of qualified polypropylene. Preferably, in the step (2), the propylene liquid phase is homopolymerized in a liquid phase polymerization vessel with an external cooler, and the propylene liquid phase is homogenized by partially vaporizing the liquid phase propylene. Part of the reaction heat is removed. The vaporized propylene gas can be cooled by an external cooler or compressed by a compressor to be recycled. Preferably, the vaporized propylene gas is condensed or compressed and returned to the propylene liquid phase for homopolymerization as a first condensate or a first recycle propylene gas.

In the present invention, the liquid phase polymerizer may be a vertical stirred reactor, and the stirring of the blades makes the reaction more uniform, and at the same time, the heat transfer between the materials is enhanced to prevent the local reaction from overheating and agglomeration. The gas-liquid two-phase coexistence in the polymerization kettle eliminates the need for high-power hybrid equipment, and the equipment has high production intensity and easy control of reaction conditions. Depending on the product to be produced or the size of the product, the polymerization kettle can also be equipped with multiple parallels, which can flexibly adjust the capacity of the device, and can also produce multi-peak polypropylene products according to the owner's requirements.

In the present invention, the reaction pressure of the gas phase homopolymerization of propylene carried out in the step (2) is lower than the reaction pressure of the liquid phase homopolymerization of the propylene. The polypropylene slurry can be continuously fed into the gas phase polymerization reactor by means of the pressure difference of the two-step reaction, and the unreacted gas phase propylene in the polypropylene slurry is continuously polymerized. The pressure difference may be 0.4 to 1.2 MPaG.

In the present invention, preferably, in the step (2), the gas phase homopolymerization temperature of the propylene is 70 to 85 ° C, the gas phase homopolymerization pressure of the propylene is 2.6 to 2.8 MPaG; and the residence time of the gas phase homopolymerization of the propylene is 45 to 60 minutes. .

In the present invention, preferably, in the step (2), the gas phase polymerization reactor is a horizontal reactor with an external cooler, and the polypropylene slurry or copolymer slurry is in the gas phase polymerization reactor. The loading is 35 to 60% by volume of the gas phase polymerization reactor.

In the present invention, the heat of polymerization generated by the gas phase homopolymerization of propylene can be removed by vaporization of the propylene chilling liquid, that is, the unreacted gas (such as propylene and hydrogen) in the above reaction passes through the upper part of the reactor. After the sedimentation removes part of the entrained polymer powder, a part of the gas is transferred to a propylene recovery system (such as a recovery tower) by adjustment, and another part of the gas is cooled by an external cooler and then enters the condensate separation tank to separate the propylene stimuli. The cold liquid is returned to the horizontal reactor through the propylene condensate pump, and then the heat of the polymerization reaction is evaporated to remove the heat of reaction. There is still unreacted propylene gas in the gas phase homopolymerization process of propylene, which can be recycled from propylene by recycling. Preferably, the propylene gas separated by the condensate separation tank is recycled to the reaction process, and the polypropylene powder inside the horizontal reactor can be fluidized for heat removal and reducing the stirring power of the reactor. The horizontal reactor is relatively long, and can be divided into 6 to 8 temperature control zones by segmental temperature control. Depending on the size of the unit and the mixing power of the horizontal reactor, the equipment for circulating the fluidized powder can be determined according to the specific conditions. Preferably, the unreacted propylene gas discharged from the gas phase polymerization reactor is condensed or compressed and returned to the propylene gas phase homopolymerization as a second condensate or a second recycle propylene gas.

In the present invention, the homopolypropylene obtained in the step (2) can be further copolymerized with ethylene and the second propylene, and the impact resistance of the polypropylene is improved by introducing the ethylene unit. Preferably, in the step (3), the amount of ethylene added is 8 to 15% by weight of the liquid phase propylene, the second amount of propylene is 15 to 20% by weight of the liquid phase propylene; and the copolymerization temperature is 65. ～80 ° C, the copolymerization pressure is 2 to 2.4 MPaG, and the copolymerization reaction residence time is 30 to 60 min.

In the present invention, the polypropylene-containing product obtained in the step (2) is separated into a polypropylene which further contains an active polymerization catalyst, and is further used in the copolymerization reaction of the step (3) without additionally adding a catalyst. The ethylene raw material for the copolymerization reaction of the step (3) does not affect the step (2). Preferably, the separation is carried out by a gas-solid separator of a series air lock mechanism at a pressure of 2 to 3 MPaG. As shown in Fig. 1, the gas lock mechanism is connected in series at the outlet of the gas-solid separator to ensure that the propylene homopolymerization carried out in the steps (1) and (2) does not interact with the ethylene-containing copolymerization reaction of the step (3).

In the step (3) of the present invention, the copolymerization reaction can be carried out in a horizontal copolymerization reactor equipped with an external cooler. The heat of polymerization generated by the copolymerization reaction can also be removed by vaporization of the propylene condensate, while the copolymerization reactor removes unreacted propylene gas, which can be recycled from propylene by recycling. During the propylene gas cycle in the step (3), a part of the propylene gas can be carried while carrying fresh hydrogen from the bottom of the copolymerization reactor into the copolymerization reactor to mix the copolymer materials in the copolymerization reactor; A propylene condensate, a feed carrying ethylene and a second propylene, is fed from the top of the copolymerization reactor. A feed of ethylene, a second propylene and hydrogen, and a recycle of propylene gas are achieved. The amount of ethylene used is relatively small and can be used up. Preferably, the feed weight ratio of ethylene to the second propylene may be 1: (1 to 2.5) to obtain impact polypropylene having better impact resistance.

In the present invention, preferably, the method further comprises: recovering the propylene gas separated in the step (3), and returning the liquid phase propylene to the liquid phase homopolymerization of the propylene in the step (2), while recovering the hydrogen gas and mixing the fresh hydrogen gas. The propylene phase is homopolymerized as the recycled hydrogen gas is returned to the step (2).

In the present invention, the pressures involved are gauge pressures.

The invention will be further described in detail in conjunction with FIG.

(A) Preparation:

The first propylene which has reached the polymerization requirement is introduced into the propylene buffer tank, and then the propylene is fed from a sole propylene outlet of the propylene buffer tank to a propylene compression pump and pressurized to 4 to 4.5 MPaG to be liquefied to obtain a liquid phase propylene having a temperature of 40 to 45 °C. The liquid phase propylene is sent to the prepolymerization tank 201 through the line 100, and at the same time, the main catalyst, the activator and the electron donor are mixed into the liquid phase propylene through the respective inlet ports on the line 100, and enter the prepolymerization tank 201 under the carrying of the liquid phase propylene. .

In this process, because the propylene prepolymerization of the present invention is combined with the liquid phase bulk polymerization of propylene and the bulk polymerization of propylene, the prepolymerization conditions used can make the propylene raw material free from freezing and cooling, and can be fed into the propylene prepolymerization, and finally the anti-polymerization. The entire preparation process of ram polypropylene reduces energy consumption and propylene loss.

(B) Polymerization system:

(1) Propylene prepolymerization: In the prepolymerization tank 201, liquid phase propylene is subjected to propylene prepolymerization under the action of a main catalyst, an activator and an electron donor. The prepolymerization tank 201 is equipped with a stirrer, the reaction temperature is 40 to 45 ° C, the reaction pressure is 3.2 to 3.9 MPaG, the reaction residence time is about 4 to 5 minutes, and the propylene polymerization ratio is about 50 to 100 times.

Prepolymerization tank feed: the main catalyst (Ti catalyst) is about 0.02 to 0.05% by weight of the liquid phase propylene, the activator (triethyl aluminum) is about 0.2 to 0.4% by weight of the liquid phase propylene, and the electron donor (cyclohexyl group) The methyldimethoxysilane is about 0.04 to 0.06% by weight of the liquid phase propylene.

(2) Liquid phase polymerization of propylene:

The raw material slurry containing the propylene prepolymer is obtained from the prepolymerization tank 201, and the liquid phase propylene and hydrogen are mixed into the liquid phase polymerization raw material through the slurry line 101, and the concentration of the polypropylene in the liquid phase polymerization raw material is 150 to 300 g/L; The amount of phase propylene added is 25 to 30% by weight of the liquid phase propylene; and the amount of hydrogen added is 0.04 to 0.3 kg with respect to 1000 kg of polypropylene in the liquid phase polymerization raw material. The liquid phase polymerization vessel 202 is a vertical reactor with agitation.

The liquid phase polymerization raw material enters the liquid phase polymerization tank 202 to carry out liquid phase homopolymerization of propylene. The liquid phase homopolymerization temperature of propylene is 65-70 ° C, the liquid-phase homopolymerization pressure of propylene is 3 to 3.8 MPaG, and the residence time is about 40 min. The level of the liquid phase polymerization raw material in the liquid phase polymerizer 202 is controlled to 45 to 57% by volume in the liquid phase polymerization vessel 202. The heat of reaction of the liquid phase homopolymerization can be carried away by the vaporization of the liquid phase propylene and the jacketed circulating water. After the vaporized part of the propylene gas is cooled by the first propylene condenser 211, the liquid is directly returned to the liquid phase polymerization tank 202, partially with The uncooled propylene gas (from the liquid phase polymerizer 202) is mixed and then enters the first condensate separation tank 212, and the separated propylene condensate is returned to the liquid phase polymerization tank 202; the separated gas phase is communicated to the circulation line 102 to The first circulating fan 213 returns to the liquid phase of the liquid phase polymerizer 202 to bubbling, and on the other hand, the gas and the reaction liquid phase are uniformly mixed, and on the other hand, the gas is lowered in the middle of the liquid phase of the polymerization vessel, and the liquid phase polymerization tank 202 is The pressure is also controlled by the amount of external circulation cooling system;

(3) Propylene gas phase polymerization:

The polypropylene slurry (containing propylene and polypropylene) discharged from the liquid phase polymerizer 202 enters the gas phase polymerization reactor 203 through a polypropylene slurry line 103 with a valve by a pressure difference, in which unreacted propylene is entrained to continue polymerization to form a polymerization. Propylene; gas phase polymerization temperature is 70 to 85 ° C, reaction pressure is 2.6 to 2.8 MPaG, and the residence time of the polypropylene slurry in the gas phase polymerization reactor 203 is about 45 to 60 min to obtain a product containing polypropylene.

The level of the material in the gas phase polymerization reactor 203 can be controlled by a radioactive level gauge or current, and the level is generally controlled within 35 to 60% by volume. The gas phase polymerization reactor 203 can be selected as a horizontal reactor with a stirrer, the material in the reactor has a uniform residence time, the equipment has high production intensity, and is highly adaptable to materials such as high-melting fingers and copolymers; the stirring paddle can be used. The “open” structure allows the powder to be evenly mixed. The heat of polymerization in the gas phase polymerization reactor 203 can be carried away by the vaporization of the propylene chill liquid and the jacketed circulating water; the unreacted propylene gas is passed through the sedimentation section of the upper portion of the gas phase polymerization reactor 203, and a part of the gas is passed. The adjustment is distributed to the propylene recovery system, and another portion of the gas is cooled by the autoclave propylene condenser 214 and the autoclave propylene cooler 215, and then returned to the gas phase polymerization reactor 203 through the first propylene condensate pump 216 to absorb the heat of polymerization. Evaporation removes the heat of reaction. The gas phase polymerization reactor 203 can adopt a sectional temperature automatic control system, and can be divided into 6 to 8 temperature control zones according to the reactor scale. The agitator also has the function of stirring and pushing the powder product forward, and the specific stirring blade angle varies according to the size and residence time of the reactor.

(4) Gas-solid separation

The polypropylene-containing product discharged from the gas phase polymerization reactor 203 is passed to a gas-solid separator 217, and unreacted propylene gas is discharged to a propylene recovery system. The separated polypropylene material also carries a non-deactivated polymerization catalyst which enters the gas lock 218 together. The air lock 218 is used to prevent the material in the subsequent copolymerization reaction from flowing back into the previous propylene homopolymerization process. The gas-solid separation is carried out at a pressure of 2 to 3 MPaG.

(5) Impact polypropylene copolymerization:

The polypropylene material from the air lock 218 is introduced into the copolymerization tank 204 and copolymerized with ethylene and the second propylene at a copolymerization temperature of 65 to 80 ° C and a copolymerization pressure of 2 to 2.4 MPaG, and the copolymerization reaction time is 30 to 60 minutes. . The heat of polymerization of the copolymerization reaction can be carried away by vaporization of the propylene chilling liquid and jacketed circulating water. A part of the unreacted propylene gas is distributed to the propylene recovery system, and another part of the gas is cooled by the second propylene condenser 219 to enter the second condensate separation tank 220, and mixed with the second condensate separation tank 220 to participate in the copolymerization reaction. The ethylene and the second propylene are added in an amount of 8 to 15% by weight of the liquid phase propylene, and the second amount of the propylene is 15 to 20% by weight of the liquid phase propylene. The recycled propylene gas separated from the second condensate separation tank 220 may be mixed with fresh hydrogen gas, and returned to the bottom of the copolymerization vessel 204 via the second circulation fan 222 to help stir the copolymer material. The gas phase polymerization reactor 203 is returned to the gas phase polymerization reactor 203, and the heat of polymerization is further absorbed to remove the heat of reaction. The propylene condensate separated by the second condensate separation tank 220 is mixed with ethylene and propylene through the second propylene condensate pump 221 to be fed from the top of the copolymerization vessel 204.

(C) Post-treatment of the copolymerization reaction product:

(A) Gas-solid separation: The copolymerization reaction product (containing propylene gas, hydrogen gas, impact polypropylene) from the copolymerization tank 204 is introduced into the degassing chamber by pressure through an outlet powder control valve.

A cyclone separator and a bag filter are arranged inside the degassing bin to separate and recover the dust in the propylene gas; the polymer powder separated from the degassing bin is dropped by gravity to the deactivator, and an appropriate amount is introduced into the deactivator. The steam deactivates the catalyst entrained in the product, and the deactivated powder enters the dryer for drying and degassing to further recover propylene.

The dryer is a horizontal indirect heating paddle stirring dryer. The hollow hot shaft and the outer jacket are all connected with low-pressure steam. The wet powder is heated and dried through the wall, and the stirring shaft can also move the wet material to the material. At the outlet, the dryer operating temperature is 100-105 ° C, and the pressure is micro-positive pressure.

(b) harvesting the polymer product: the deactivated, dried powder falls from the dryer to the displacement vessel by gravity, and the hot nitrogen gas supplied by the nitrogen heater is further removed from the displacement vessel to further remove a trace amount of propylene gas entrained in the powder; The exhausted gas is discharged to the high level after passing through the water-sealing tank and the flame arrester; the degassed powder is sent to the subsequent section through the nitrogen air supply system to obtain the final impact polypropylene product.

(C) Propylene recovery system: The propylene gas released by heating the wet powder in the dryer is filtered through a filter on a dryer and then washed into a water washing tower. The water washing tower uses demineralized water as the washing medium, and the gas contains a trace amount of hydrogen chloride decomposed by the catalyst. Therefore, an appropriate amount of alkali liquid and hydrochloric acid in the water are added to the desalted water. The washed propylene gas is cooled by a water washing tower cooler, and then recovered by pressurization by a propylene recovery compressor, and can be used for external delivery.

The propylene gas separated from the degassing chamber is propylene gas discharged from the homogenization of the gas phase propylene, and the propylene gas discharged from the copolymerization reaction is buffered, then washed into the oil washing tower, and then compressed by the propylene gas compressor into the high pressure propylene scrubber to separate the heavy components. The propylene gas separated from the top of the high-pressure propylene scrubbing tower is further sent to the dehydrogenation tower to remove hydrogen-rich gas, and the liquid-phase propylene obtained by condensing and separating the hydrogen-rich propylene condenser is separated from the tower and returned to the dehydrogenation tower as a reflux liquid. After the hydrogen is mixed with the metered fresh hydrogen, it is pressurized by the circulating hydrogen compressor and sent to the liquid phase polymerization tank 202 for use; the dehydrogenation tower bottom condensate is buffered into the propylene condensate tank, and then pressurized by the recovery propylene condensate pump. The latter part is returned to the liquid phase polymerization tank 202 for use as part of the overhead reflux liquid of the high pressure propylene scrubber; the propylene containing a large amount of propane (about 19% by weight of propane) leaving the bottom of the high pressure propylene scrubbing tower is filtered and recovered with a propylene recovery compressor. The pressurized aqueous propylene is mixed and sent to the boundary zone for treatment.

Wherein, the oil washing tower is a plate tower with a washing tower condenser at the top, and the propylene gas is washed with white oil containing an antistatic agent for removing the aluminum alkyl and oligomerization entrained in the propylene gas. Impurities such as matter. The high-pressure propylene scrubber is a sieve plate rectification column with a reboiler at the bottom, and the propylene condensate of the propylene condensate tank is used as a reflux liquid for separating propane in the propylene to prevent the accumulation of propane in the system; the dehydrogenation tower Is a sieve tray tower connected in series after the high-pressure propylene scrubber, and the condensed liquid of the propylene condenser is used as a reflux liquid of the dehydrogenation tower to cool the propylene in the dehydrogenation tower for separating the hydrogen-rich gas contained in the propylene gas, and the dehydrogenation tower The bottom is in direct communication with the propylene condensate tank, and the reflux liquid condenses and directly enters the propylene condensate tank.

The invention will be described in detail below by way of examples.

The impact polypropylene was tested for impact strength of the notched simply supported beam by GB/T 1043.1-2008, and the elastomer content was determined by heptane extraction.

Example 1

Follow the process shown in Figure 1:

(1) Prepolymerization

The first propylene is pressurized to a liquid phase propylene having a pressure of about 4.2 MPaG and a temperature of 42 ° C; and the liquid propylene is used as a carrier, and a Ti catalyst (CS-1) having a content of 0.04% by weight in the liquid phase propylene is separately added. 0.3% by weight of triethylaluminum and 0.05% by weight of cyclohexylmethyldimethoxysilane; all were directly input into the prepolymerization kettle to form a polymerization slurry, followed by a condition of 42 ° C, 3.2 MPaG, and a residence time of 4 min. The propylene prepolymerization is carried out, and the polymerization ratio of the polypropylene in the obtained raw material slurry is 75 times;

(2) Liquid phase bulk polymerization

The raw material slurry obtained in (1) is added to the recovered liquid phase propylene and hydrogen mixed into a liquid phase polymerization raw material (wherein the concentration of the polypropylene is 200 g/L, and the amount of the recovered liquid phase propylene is about 25% by weight of the liquid phase propylene, and the amount of hydrogen added is For 0.08kg/1000kg polypropylene), the liquid phase homopolymerization of propylene is carried out at 68 ° C and 3 MPaG, and the level in the reaction kettle is 45 vol%, and the residence time is 40 min;

During the liquid phase homopolymerization of propylene, part of the liquid phase propylene vaporization carries away part of the polymerization heat. The vaporized propylene gas is recovered and returned to the propylene liquid phase homopolymerization in a gas phase or a liquid phase.

(3) Gas phase bulk polymerization

The polypropylene slurry obtained in (2) was charged into a gas phase bulk polymerization reactor, and propylene gas phase homopolymerization was carried out at 80 ° C and 2.6 MPaG for a residence time of 45 minutes, and the material level in the reactor was 55 vol%.

During the gas phase homopolymerization of propylene, a part of the unreacted propylene gas discharged is recovered, and is returned to the gas phase homopolymerization of the propylene in a gas phase or a liquid phase.

(4) The polypropylene-containing product obtained in (3) was subjected to gas-solid separation at 2.6 MPaG. Then, the obtained polypropylene is copolymerized with a second amount of ethylene in an amount of 15% by weight of liquid phase propylene and 18% by weight of liquid phase propylene in a copolymerization kettle at 65 ° C and 2.4 MPaG, and the residence time is 45 minutes. , a copolymerization product is obtained.

(5) The copolymerization product is dried to obtain impact polypropylene.

The recovered propylene and hydrogen are returned for bulk bulk polymerization.

In the calculation of the above process, the unit energy consumption for producing impact polypropylene is 62 kg of standard oil per ton of impact polypropylene. Production of 1000kg impact polypropylene, propylene loss of 4kg.

The impact polypropylene was evaluated for performance, and the elastomer content was 46% by weight or more. The toughness of the impact polypropylene was large, and the impact strength of the notched simply supported beam was not broken at 23 ° C and -23 ° C.

Example 2

Follow the process shown in Figure 1:

(1) Prepolymerization

The first propylene is pressurized to a liquid phase propylene having a pressure of about 4 MPaG and a temperature of 45 ° C; and the liquid propylene is used as a carrier, and a Ti catalyst (CS-1) having a content of 0.06% by weight in the liquid phase propylene is separately added, 0.2% by weight of triethylaluminum and 0.06% by weight of cyclohexylmethyldimethoxysilane; then all directly into the prepolymerization kettle to form a polymerization slurry, followed by 45 ° C, 3.6 MPaG, residence time 4 min Performing propylene prepolymerization, the polymerization ratio of the polypropylene in the obtained raw material slurry is 50 times;

(2) Liquid phase bulk polymerization

The raw material slurry obtained in (1) is added to recover the mixed raw material of propylene and hydrogen into a liquid phase polymerization raw material (wherein the concentration of polypropylene is 150 g/L, the amount of recycled propylene is about 27% by weight of liquid phase propylene, and the amount of hydrogen added is 0.12 kg/ 1000kg polypropylene), liquid phase homopolymerization of propylene at 70 ° C, 3.5MPaG, the reactor level is 60% by volume, staying for 35min;

(3) Gas phase bulk polymerization

The polypropylene slurry obtained in (2) was charged into a gas phase bulk polymerization reactor, and gas phase homopolymerization of propylene was carried out at 65 ° C and 2.7 MPaG for a residence time of 60 minutes, and the level in the reactor was 45% by volume.

(4) The polypropylene-containing product obtained in (3) was subjected to gas-solid separation at 2.4 MPaG. Further, the obtained polypropylene is copolymerized with a second amount of ethylene in an amount of 10% by weight of liquid phase propylene and 20% by weight of liquid phase propylene in a copolymerization kettle at 80 ° C and 2.2 MPaG, and the residence time is 60 minutes. , a copolymerization product is obtained.

(5) The copolymerization product is dried to obtain impact polypropylene.

The propylene and hydrogen are recovered and continue to be used for liquid phase bulk polymerization.

In the calculation of the above process, the unit energy consumption for producing impact polypropylene is 45 kg of standard oil per ton of impact polypropylene. Production of 1000kg impact polypropylene, propylene loss of 5kg.

The performance of the impact polypropylene was evaluated. The impact strength of the notched simple beam was 62 (kJ/m ² , 23 ° C), 6.4 (kJ/m ² , -23 ° C), and the elastomer content was 21.6% by weight.

Example 3

Follow the process shown in Figure 1:

(1) Prepolymerization

The first propylene is pressurized to a liquid phase propylene having a pressure of about 4.5 MPaG and a temperature of 40 ° C; and the liquid propylene is used as a carrier, and a Ti catalyst (CS-1) having a content of 0.05% by weight in the liquid phase propylene is separately added. 0.4% by weight of triethylaluminum and 0.04% by weight of cyclohexylmethyldimethoxysilane; then all directly into the prepolymerization kettle to form a polymerization slurry, followed by a condition of 40 ° C, 3.8 MPaG, and a residence time of 5 min. The propylene prepolymerization is carried out, and the polymerization ratio of the polypropylene in the obtained raw material slurry is 100 times;

(2) Liquid phase bulk polymerization

The raw material slurry obtained in (1) is added to recover the mixed raw material of propylene and hydrogen to form a liquid phase polymerization raw material (wherein the concentration of polypropylene is 300 g/L, the amount of recycled propylene is about 30% by weight of liquid phase propylene, and the amount of hydrogen added is 0.2 kg/ 1000kg polypropylene), liquid phase homopolymerization of propylene at 69 ° C, 3.7 MPaG, the reactor level is 40% by volume, stay 45 minutes;

(3) Gas phase bulk polymerization

The polypropylene slurry obtained in (2) was charged into a gas phase bulk polymerization reactor, and gas phase homopolymerization of propylene was carried out at 70 ° C and 2.8 MPaG for a residence time of 48 minutes, and the level in the reactor was 50% by volume.

(4) The polypropylene-containing product obtained in (3) is subjected to gas-solid separation at 2.8 MPaG, and the obtained polypropylene is used in an amount of 8 wt% of ethylene in liquid phase propylene, and the amount is 15 wt% of liquid phase propylene. The second propylene was copolymerized in a copolymerization vessel at 70 ° C and 2.0 MPaG for a residence time of 30 minutes to obtain a copolymerization product.

(5) The copolymerization product is dried to obtain impact polypropylene.

In the calculation of the above process, the unit energy consumption for producing impact polypropylene is 50 kg of standard oil per ton of impact polypropylene. Production of 1000kg impact polypropylene, propylene loss of 5kg.

The performance of the impact polypropylene was evaluated. The impact strength of the notched simple beam was 36 (kJ/m ² , 23 ° C), 4.4 (kJ/m ² , -23 ° C), and the elastomer content was 15.8% by weight.

Comparative example 1

(1) Prepolymerization

50% by weight of liquid phase propylene at -5 ° C and 3.81 MPaG was mixed with a polymerization catalyst, and the polymerization catalyst contained 0.08 wt% of Ti catalyst (CS-1) based on total liquid phase propylene, and 0.5 wt% of triethylbenzene. Base aluminum and 0.08 wt% cyclohexylmethyldimethoxysilane are added to the prepolymerized polytube for low temperature prepolymerization, the prepolymerization temperature is about 10 ° C, the prepolymerization pressure is about 3.8 MPaG, and the residence time is 12 min. The polymerization ratio of polypropylene in the raw material slurry is about 60 times;

(2) Liquid phase bulk polymerization

The raw material slurry was mixed with the remaining 50% by weight of liquid phase propylene (concentration of polypropylene 50% by weight, hydrogen added to 0.08 kg / 1000 kg of polypropylene) into a liquid phase polymerization raw material, and then entered into the first loop reactor. A part of the propylene in the liquid phase polymerization raw material is polymerized, and the remaining liquid is used as a diluent of the polymer to make the material in the reactor slurry, and the circulation is performed by the axial flow pump, and the slurry is kept flowing at a high speed and uniformly mixed in the reactor. ;

The slurry in the first loop reactor was continuously fed to the second loop reactor through a discharge-only line to continue liquid phase polymerization and to replenish fresh propylene (added in an amount of 25% by weight of liquid phase propylene). The first and second loop reactors have a reaction temperature of about 70 to 73 ° C, a reaction pressure of about 3.8 MPaG, and a residence time of about 1 h.

(3) Copolymerization with ethylene

The polymerization slurry discharged from the second loop reactor was subjected to gas-solid separation at 2.6 MPaG. Further, the obtained polypropylene is copolymerized with a second amount of ethylene in an amount of 8 wt% of liquid phase propylene and 15 wt% of liquid phase propylene in a copolymerization kettle at 70 ° C and 2.0 MPaG for a residence time of 30 min. , a copolymerization product is obtained.

The copolymerization product was dried to obtain an impact polypropylene.

By calculating the above-mentioned loop polymerization process, the unit energy consumption for producing impact polypropylene is about 70 kg of standard oil per ton of impact polypropylene. Production of 1000kg impact polypropylene, propylene loss of 5kg.

The performance of the impact polypropylene was evaluated. The impact strength of the notched simple beam was 38 (kJ/m ² , 23 ° C), 4.4 (kJ/m ² , -23 ° C), and the elastomer content was 14.8% by weight.

The above-mentioned loop reactor and process are currently used in many propylene polymerization reactors and processes at home and abroad, although it is also possible to prepare impact polypropylene, but since the loop tube reactor is completely removed by the jacket circulating water, the slurry The flow in the loop is realized by the axial flow pump. The polypropylene slurry is flashed out in the liquid phase, and the steam heating system must be added to further increase the energy consumption of the process.

Comparative example 2

After pressurizing propylene to 3.5 MPa and condensing to -5 ° C, the liquid phase enters the prepolymerization vessel, and the polymerization catalyst (including Ti catalyst (CS-1), triethyl aluminum, cyclohexylmethyl dimethoxy silane At a contact temperature of 0 ° C, the content of each component of the catalyst in the liquid phase propylene was 0.08% by weight of Ti catalyst (CS-1), 0.5% by weight of triethylaluminum and 0.08% by weight of cyclohexylmethyldimethoxy The silane is mixed with a stirrer, and the active center of the catalyst is formed, and then the prepolymerization of propylene is started. The residence time of the prepolymerization is 5 min, and the polymerization ratio of the polypropylene in the obtained raw material slurry is 75 times.

The prepolymerized slurry containing the active catalyst and the propylene mixture was introduced into a liquid phase polymerization vessel, and the reaction was continued at 69 ° C and 3.4 MPa for 1 to 1.6 hours. The concentration of polypropylene in the slurry was 130 g/L, the total amount of propylene was 10 t/h, and the amount of hydrogen added was 150 L/min. The level in the liquid phase reactor was 45% by volume.

A polymerization catalyst was further added to the liquid phase polymerization: Ti catalyst (CS-1) 0.4 g/h, triethyl aluminum 3 L/h, and cyclohexylmethyldimethoxysilane 0.4 L/h.

The slurry discharged from the liquid phase polymerizer enters the gas phase reaction vessel, and is subjected to gas phase bulk polymerization at 90 ° C and 2.8 MPa, and the residence time is 1.5 hours, and the level in the gas phase reactor is 40% by volume.

After completion of gas phase homopolymerization of propylene, the obtained product containing propylene homopolymer was subjected to gas-solid separation at 2.6 MPaG. Further, the obtained polypropylene is copolymerized with a second amount of ethylene in an amount of 8 wt% of liquid phase propylene and 15 wt% of liquid phase propylene in a copolymerization kettle at 70 ° C and 2.0 MPaG for a residence time of 30 min. , a copolymerization product is obtained.

The copolymerization product was dried to obtain an impact polypropylene.

In the calculation of the above process, the unit energy consumption for producing impact polypropylene is 60 kg of standard oil per ton of impact polypropylene. Production of 1000kg impact polypropylene, propylene loss of 6kg.

It can be seen from the results of the above examples and comparative examples that the method provided by the present invention combines propylene prepolymerization, propylene liquid phase bulk polymerization and propylene vapor phase bulk polymerization to carry out polymerization of homopolypropylene, which can simplify the process without propylene condensation. . The liquid phase propylene is all involved in the prepolymerization, and the amount of the main catalyst added is reduced, thereby obtaining a better raw material slurry in which the propylene prepolymer is dispersed, which is advantageous for improving the product quality. The prepolymerization of propylene is carried out at a mild temperature of 40 to 45 ° C, which can ultimately reduce the unit energy consumption and propylene loss of the entire production of impact polypropylene.

In Comparative Example 1, propylene needs to be condensed to below zero, and only part of the liquid phase propylene can be subjected to low temperature prepolymerization; fresh propylene and a polymerization catalyst need to be added during the polymerization, and the product needs to be flashed, although impact polypropylene can also be prepared, but The propylene polymerization unit product consumes a large amount of energy and propylene loss throughout the process.

In Comparative Example 2, the prior art requires propylene to be condensed to below zero, and the prepolymerization temperature is low, the catalyst is added in a high amount, and a polymerization catalyst is added, although the impact polypropylene can also be prepared, but the propylene polymerization unit of the entire process is completed. Product energy consumption and propylene loss are high.

The prior art requires propylene condensation to zero for low temperature prepolymerization. If other conditions are still carried out in accordance with the conditions of Example 1, the impact polypropylene is polymerized, and the impact polypropylene having the same specifications as in Example 1 will not be obtained. To obtain the impact polypropylene of the same specification as in Example 1, it is necessary to increase the amount of the catalyst, adjust the polymerization conditions, increase the energy consumption and propylene loss of the propylene polymerization unit product which completes the entire process, and increase the cost of the catalyst.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the invention is not limited thereto. Within the scope of the technical idea of the present invention, various simple modifications can be made to the technical solutions of the present invention, including various technical features combined in any other suitable manner, and these simple variations and combinations should also be regarded as the disclosure of the present invention. All fall within the scope of protection of the present invention.

Claims

A method of polymerizing impact polypropylene, the method comprising:

(1) compressing the first propylene into liquid phase propylene, and mixing the polymerization catalyst into a prepolymerization reactor for prepolymerization of propylene to obtain a raw material slurry containing a propylene prepolymer;

Wherein, the prepolymerization temperature is 40 to 45 ° C, and the prepolymerization pressure is 3.2 to 3.9 MPaG;

The polymerization catalyst comprises a main catalyst, an activator and an electron donor, the main catalyst being used in an amount of 0.02 to 0.05% by weight of the liquid phase propylene;

(2) mixing the raw material slurry, the recovered liquid phase propylene and the recycled circulating hydrogen into a liquid phase polymerization raw material, and feeding it into a liquid phase polymerization tank for liquid phase homopolymerization of propylene to obtain a polypropylene slurry; Continuously input into the gas phase polymerization reactor, and the propylene in the polypropylene slurry is subjected to gas phase homopolymerization of propylene to obtain a polypropylene-containing product;

(3) separating the polypropylene-containing product, and copolymerizing the separated polypropylene with ethylene and second propylene to obtain impact polypropylene.
The method according to claim 1, wherein in the step (1), the activator and the electron donor are used in an amount of 0.2 to 0.4% by weight and 0.04 to 0.06% by weight, respectively, of the liquid phase propylene.
The method according to claim 1, wherein in the step (1), the liquid phase propylene pressure is 4 to 4.5 MPaG, and the liquid phase propylene temperature is 40 to 45 ° C;

Preferably, the residence time of the propylene prepolymerization is 4 to 5 min;

Preferably, the propylene prepolymer is a polypropylene having a polymerization ratio of 50 to 100 times.
The method according to claim 1, wherein in the step (2), the concentration of the polypropylene in the liquid phase polymerization raw material is 150 to 300 g/L; and the amount of the recovered liquid phase propylene added is the liquid phase. 25 to 30% by weight of propylene; and the amount of hydrogen added is 0.04 to 0.3 kg with respect to 1000 kg of polypropylene in the liquid phase polymerization raw material.
The method according to any one of claims 1 to 4, wherein in the step (2), the liquid phase homopolymerization temperature of the propylene is 65 to 70 ° C, and the liquid phase homopolymerization pressure of the propylene is 3 to 3.8 MPaG. The residence time of the liquid phase homopolymerization of propylene is 35 to 45 min.
The method according to any one of claims 1 to 4, wherein in the step (2), the propylene liquid phase is homopolymerized in a liquid phase polymerization vessel with an external cooler, and is partially described The manner in which the liquid phase propylene is vaporized removes heat from the partial reaction heat of the liquid phase homopolymerization of the propylene;

Preferably, the vaporized propylene gas is condensed or compressed and returned to the propylene liquid phase for homopolymerization as a first condensate or a first recycle propylene gas.
The method according to any one of claims 1 to 4, wherein, in the step (2), the propylene gas phase homopolymerization temperature is 70 to 85 ° C, the propylene gas phase homopolymerization pressure is 2.6 to 2.8 MPaG; and the propylene is carried out. The residence time of gas phase homopolymerization is 45 to 60 min.
The method according to any one of claims 1 to 4, wherein in the step (2), the gas phase polymerization reactor is a horizontal reactor with an external cooler, and the polypropylene slurry is in the The volume of the gas phase polymerization reactor is 35 to 60% by volume of the gas phase polymerization reactor;

Preferably, the unreacted propylene gas discharged from the gas phase polymerization reactor is condensed or compressed and returned to the propylene gas phase homopolymerization as a second condensate or a second recycle propylene gas.
The method according to any one of claims 1 to 4, wherein, in the step (3), the amount of ethylene added is 8 to 15% by weight of the liquid phase propylene, and the amount of the second propylene added is 15 to 20% by weight of liquid phase propylene; copolymerization temperature of 65 to 80 ° C, copolymerization pressure of 2 to 2.4 MPaG, and copolymerization reaction residence time of 30 to 60 minutes.
The method according to any one of claims 1 to 4, wherein in the step (3), the separation is carried out by a gas-solid separator of a series air lock mechanism at a pressure of 2 to 3 MPaG.